Two-stroke-cycle opposed-piston internal-combustion engine



y W. B. BRONANDER. Two-STROKE cYcLE oPPosED PlsToN INTERNAL coNusTloN ENGINE.

APPLICATION FILED SEPT. 26, 1919- M3293@ Pimm/ed 60% 317, )1922.

. W. B. BRONANDER.

Two-STROKE cYcLE oPPosEn PlsoN INTERNAL coNausTloN ENGINE.

APPLICATION FILED SEPT. 26, l9l9.

@Nwe/wibo@ M5 Brom/valer e n@ @Moms/ S w. summum.

'TWO-STROKE CYCLE OPPOSED PISTON INTERNAL COIIIBUSTIOII ENGINE.

APPLICATION FILED SEPT- 26, |9I9.

3 SHEETS-SHEET 3.

194323,@@0 l Tamm m5111192@ Patented @et il?, lilggo WILHELM BERTIL BRONANDER', OF MONTCLAER, 'NEW JERSEY.

TWO-STROKE-CYCLE OPPOSED--STON TERNAL-COMBUSTIOT ENG-INE.

Application tiled September 26, 1919. Serial No. j,

To a/,Z 'Lo/0m it' may concern Be it known that l, lrnninuifi Bnnrin Bilo- NANDER, a citizen of the United States, residing at Montclair', in the county of Essex, State of New Jersey, have invented certain new" and uset'ul improvements in Two- Stroke-('Lycle Opposed-Piston internal-Combustion Engines; and I do hereby declare the following to be a full, clear, and exact description oi the invention, such as will enable others skilled in the art to which it apperf tains, to make and use the saine.

This invention relates to improvements in two-stroke-cycle opposed-piston internal combustion engines in which the pistons are utilized for" controlling the cylinder ports and the ch arge ot' fuel is given a preliminary compression before being introduced into the cylinders between the pistons.

ln my copending application, Serial No. 312,688, iiled July 23, 1919, there is disclosed an engine which overcomes-thtJ disadvantages of the usual types of two-strolie-cycle engines in which the pistons are utilized torA conti'ollingports in the walls of'the cylinders.

kThese prior engines, as usually constructed,

comprise a number of separate cylinders each provided with inlet ports which are uncovered by the piston as it approaches the bottom of the cylinder to allow a charge of gas, which has been given an initial compression to enter the cylinder. Each cylinder is also provided with exhaust ports' which must be so arranged with respect to the inlet ports that they are uncovered before the inlet ports, as the piston approaches the bottom of the cylinder to permit the greater portion of the waste gases to escape before the inlet ports are uncovered. When the inlet ports are uncovered, a charge of gas under pressure will enter the cylinder and aid in sweeping out the waste products, but on account of the arrangement of the inlet and exhaust ports the latter will not be covered until an appreciable time after theinlet ports have been closed by the piston as it moves upward 'on the next stroke, so that 'some of the charge may escape fromthe exhaust ports, the amount depending upon the interval between the closing of the two sets of ports as determined by the speed of the engine, Due to the escape of more or less of the charge, the advantages of its initial compression are. in a measure, lost and the ef- `ticiency of the engine is correspondingly reduced. i

The invention covered by ymy copending application referred to above comprises a two-stroke-cycle internal combustion engine in which each powerunit comprises a pair of communicating cylinders ,each provided with a piston. rlhe piston oit oned of the cylinders controls exhaust ports in the wall of of the cylinder and also. carburetor or supply ports through which the gas is supplied to the crank case of the engine. rlheother piston controls inlet ports in the wall of the other cylinder through which a charge, is usupplied to thecylinders after being given an initial compression in the crank' case of the engine. 'The two pistons of each unit are connected to the crank shaft of the engine in such a manner as to cause the piston controlling the exhaust ports to uncover these ports before the-piston in the other cylinder has uncovered the inlet ports on the working strokes. of the pistons, and on the reverse or compression' strokes the piston controlling the exhaust ports will again travel in advance of the other piston so as to cover the exhaust ports before the'other piston has covered the inlet ports. There is thus an interval during which both the exhaust and inlet ports will be open so that the incoming charge of compressed gas will sweep out of the cylinders such ,waste gases as did not escape when the exhaust ports were first uncovered. Y

Various types of internal combustion engines in which' two pistons are arranged in a common cylinder so as to work in opposite directions, have been constructed, the general object of these arrangements being to obtain double the power of a gas engine of the saine kind without increasing the diameters of the cylinders and with a lesser number yof working parts than would be re# quired were the saine increase in power obtained by providing additional separate cylinders with their necessary adjuncts. As

these engines have usually been constructed,

each power unit comprises a single elongated cylinder having near one end a series of exhaust ports which are controlled by one of the pistons, and near the other end a series of ports through which scavenging air is introduced and beyond these ports a series of inlet ports through which the fuel charge is supplied, bothof these series of ports being controlled by the other piston. Two-stroke-cycle enginesof this general construction are open to the same objections as are the types' of two-'stroke-cycle engines de'- scribed above in which a single piston controls" both the exhaust and inlet portsI in thel same cylinder, namely, that theexhaustports must be arranged to loe-uncovered by one of the pistons before the inlet ports are uncovered by the other piston to permit the waste gases to escape as the pistons move apart during their working stroke, and

since the exhaust ports are uncovered before the' inlet ports, they will remain open after the inlet ports have been closed during the opposite or compression stroke of the pistons.

' There is escape through the exhaust ports, and the slower the speed of the engine the greater will be the amount of charge that may escape. As in the case of single piston engines, the advantage of the initial compression of the fuel is thus-in a measure lost', and the efiiciency of the engine is correspondingly reduced. J

Various attempts have been made ,toevercome this defect in engines of this type, such as throttling devicesor valves adapted to be operated in such a manner as to permit a free -discharge of the products of combustion during the earlier part of the exhaust period and to check the exhaust outlet' to allow the ,building up of pressure of the incoming charge so that the advantagesy of the initial compression of the charge are retained. Such arrangements, however, re-

complicated quire the provision of relativel ci in timed revalves which must be operate lation to the'other parts of thel engine and' are inaddition usually made responsive to the load on the-engine, as by being controlled by a governor so as to vary the throttling effect in accordance with 'the demands upon the invention ofthe companion application each power unit of the engine comprises a pair of elongated,parallel cylinders which are in communication with each other at a point midway between their ends'and in each of which is a pair of pistonsl adapted to move in opposite d/irections; The ends of these cylinders arev in communica-tion with gas-tight crank cases int'which the preliminafry' compression of the fuel charge..

'takes place and whichI are yadapted to be` placedm communication with `the cylinders throughtwo series'ofinlet'portsin the walls of the cylinders, which are controlled by' accordingly, a possibility that -sorne of the charge 'supplied to the cylinder will two of the four pistons of the unit. The charges ofA fuel are admitted to the crank eases through supply -ports in the walls of the cylinders, which are' uncovered by the othrvtwo pistons when the are at the inner ends of their strokes.` Ad]acen't tlie supply ports, but nearer the center of the cylinders are exhaust ports which are uncovered by the sameps'tons that control the supply ports, when these pistons are at the outer ends of their strokes.

"The pistons are connected in pairs to two crank shafts of the engine in such a manner thatas they move outwardly on the working stroke the two pistons that control the exhaust ports will uncover these ports before the two pistons that control thel inlet ports have uncovered the-latter ports, and on the reverse or compression stroke the piston controlling the exhaust ports will again travel in advance of the other piston so as to cover the exhaust ports before the latter pistons have covered the inlet'ports. There is, accord-v ingly, anv interval during which all of the exhaust and inlet ports aresimultaneously opened so that the charges of compressed y gas which are permitted to enter'- the cyl` inders will sweep out such waste gases as did not escape when the exhaust ports were first uncovered. The gases will rush through the cylinders-and through the opening between them and ,eii'eet'ively scavenge all parts of the same.. Since `the exhaust ports are always closed before the inlet ports there is' no diminution of pressure, and the compression under whichthe gas is supplied to the spaces between the pistons is maintained.` The arrangement possesses the further advantage that it avoids the use ofall projections or baffles such as are frequently provided at the tops of pistons in engines of the two-stroke-cy'cle type in which each pistoncontrols inlet and exhaust ports in the walls of the same cylinder, and which tend to cause the formation of pockets of gas. Furthermore, the manner in which the pistons are connected tov the crank shafts permits a longer stroke with the same throw of the cranks than could' be obtained-by a single piston connected toa crank shaft in the vusual manner.

` As disclosed in my companion application Serial No. 326,589, the preferred. emi bodiment: of the invention comprises an engine in which one series of inlet ports is arranged in. the wall of one of the cylinders toward the end ofthe cylinderv that com- 'municates withone of the crank cases while the other series of inlet ports is correspondinvly`arranged in the wall of the other cylinder toward the end that communicates with the-other crank case, adjacent carburetor and exhaust ports lbeingplaced at the end of each cylinder opposite to the end at which Ithe inlet ports are placed.

naeaaao With this arrangement of` the ports.` it i by which they are connected to the pistons.

shall cause the pistons to-control the ports in the desired manner. ln many cases it may be required that the shafts be driven in opposite directions, and the present application is directed particularly to an embodiment of the invention of my companion application which meets this requirement and also provides for other modifications in the arrangements of the ports, which may be' desirable in practice.

In accordance with the present invention both series of inlet ports -are arranged toward opposite ends of one cylinder and are controlled by the two pistons therein, while, the two sets of adjacent exhaust and su ply ports are arranged toward opposite ends `of the other cylinder and are controlled by A'the two pistons therein. Thetwo cylinders are in communication so that incoming fuel charge may pass from the first named' cylinder into the other, while the waste gases` also follow the same course to reach the exhaust ports. W' ith this arrangement of the ports the shafts must rotate in opposite directions in order that the pistons vmay funetion in accordance with the invention.

The particular nature of the invention, as well as other objects and advantages thereof, will appear more clearly from a description of a preferred embodiment as shown in the accompanying drawings in which 4 Fig. l is a longitudinal section through one of the power units' of the engine at ri ht angles to the crank shafts;

ig..2 is a transverse section of the unit V along the line 2 2 of Fig. 1g,

F ig. 3 is a similar. section along the line 3 3 of Fig. l; and

Figs. 4 to 7 inclusive are diagrams showing successive positions'of the moving parts of the engine.

lt will be understood that the engine ma)f be composed of as many units as desired, but since these units are all of the same construction only one of them has been shown in the drawings and will be described in the following specification. ln the drawings, in which similar reference characters denote similar parts throughout. the several views, 20 is a casing provided with a pair of circular inner walls 21 which mergeA together as at 22, thus forming a pair of elongated, adjacent, parallel cylinders and B separated by a center wall, which at a point'l ng li uid may be circulated by means of suitab e pipe connect-ions. At each end of the casing, the -wall 24' is carried outwardly as at 25, and the ends of the chamber are formed by partitions 26, so that there is thus formed in each end of ther casing a space which is divided into two chambers-27 and 23 by' a partition 29 extending from the wall 22 between the cylinders to the outer wall 24: and the corresponding partitions 26 as shown most clearly in Figs. 2 and 3. 'lhc outer ends of the chambers 27 are in communicationwith the interiors of gas-tight crank cases 30 attached to the ends of the casing in any suitable manner. rlhe inner ends of both chambers 27 are in communication with cylinder A through a number ot inlet ports 3l. The two chambers 28 communicate with the other cylinder B through exhaust ports 32, and at the side of the casing the chambers are provided with enlarged .ports 33 to which exhaust manifolds may be connected, it being understood that the manifolds of each unit may merge into a common manifold to which the manifolds of the other units of the engine may also be connected. Between the exhaust ports 32, and the ends of cylinder B are supply ports 34 which communicate with chambers 35 formed between the wall of this cylinder and the outerY wall of casing 2O and each separated from the adjacent chamber 28 by a partition 36. Each of the chambers 35 is provided with an enlarged port 37 adapted to be connected to a gas-supply manifold, and as in the case of the exhaust manifolds, the supply manifolds of each unit may merge into a common manifold leading to a carburetor. The heat transmitted through the partitions` 36 from the exhaust gases discharged through the p orts 32 will raise the temperature of the incoming fuel charges. Each of the cylinders is provided at av point'midwav between its endswith a suitable4` spark plug 38 for igniting the charge within the cylinder.

Mounted in suitable bearings at opposite ends of the unit are shafts 39, it being understood that these shafts'are common to the severall units of which the engine is composed and each is providedl at the points where it passes through the walls of the crank cases with suitable bushing to prevent escape of gas from the crank cases. Each of the shafts 39 is provided with cranks 4()- for each unit of the engine, and' each crank has a pin 41 upon which is j ournaled a member 42 having extended ends to one of which is rigidly attached, as. by being formed integrally therewith, a connecting rod 43 which is pivotally attached as at 44`to one ofthe pistons 45 of one cylinder. Attached l attached to the companion piston 48 of the other cylinder. It is necessary to provide a pivotal connection between one ofthe connecting rods and the member 42 attached to" the crank pin to allow for slight'variations in .the parallelism of the two:v connecting rods which occur during the'movement otthe parts. v Y

It "s necessary that the two main shafts be connected' to eachother in order that the correct voperative relationf between :both pairs of pistons -shzallbe maintain@d'.A- As'. indicated/on the'l -drawin i this connection comprises atransverses aft 49' geared to each of the main shafts 39" by suitable bevel o r other gears; butit will; be 'understood thatany other; suitable arrangement may be em'- ployedV 'for .connecting thel main shafts'- te each other; f y

It will 'he' seen=from the above descri tion of" the apparatus that'there is'provi edl a f twinLcy-l-inder opposed-piston power unit in? whichthe'halve's oif'the unit* are of similar construction-,fand the corre onding ports andpistons are Jso arranged't at the pistone of' cylinderAr control the two'sets of inletports 31- orf-:the unit, and the pistons' of cylnder 1Bfeontrol" the two sets of exhaust ports-322 and carburetor ports 3430i' this cylinder, while vboth pairs 'of companion pis-"i` tous are ctfnne'cted to the crank shafts* inni-fA manner similar "to thatshown 'ini my' 'cd-w pendngapplication, Serial No. B125`688.-

The loperation off thelenginecan -be' efxplained'lnystE clearly by the aid ofl the .diasy grams 'of Figs; 4to 7 inclusive.; Assuming i th'atboth of the crank pins ofthe'unit are at 'their inner dead centers each pair of companion pistons will be at) the innerlimits'lof their strokes and their'- faces will be iny the same plana@v The two crank shafts are assumedto be rotatingy in the directions indi catedby the arrows inFigs: 4 to 7 7inclusive.

o@ passedft 'eir'dead centers, -for the slight cutie in;

Asv the/crankl pins of both pairs of pistons move away from their dead center points, the pistons 45 in cylinder-B will move out wa'rdly a slight' amount, while the companion pistens48fin cylinder will move slightly toward each other, and Fig". 4 shows the positions of the pistons at this stage of operation.

plosion should take place when the case is under greatest compression, as it is when the piston is at the limit ofits inward stroke, but at this time the crank to which theupiston I is'connected will be ondead center and some power will be lost when the charge is then fired. lt is of advantage to lhave the explosion occur immediately after the crank has passed over the dead center7 butA there willthen be a loss in the, compression of the chargedue to the increased space in the cyl# g f inder.' With the prescritl arrangement lgnirrs inner deadcenter;

tionLA ma '--take place-1 atten the i crankslhaveu incasso- Y ward movement of ypistons 45y isfcompensated by a corresponding inward movement of pis.-

tons 48; so that the charge of gas between y' the opposed pistons is kept under` maximum compression at the instant oi' firing, therey being communication between the two cylindersithrough aperture 23 so the pressure is `eolualized. i

generalrelationshown in Fig. 1.l When the v pistons 45 are at the inner ends of their strokes, both sets ofI carburetor ports 34 will beuncovered to permita fuel 'charge to pass into 'each-crank case;v .As-each vpiston 45 y moves-foutwar it coversthe'correspondingl ports 34,. andy sfnce thacorresponding linlet ports` 31- are covered by the 'pistons 48,11 the chargestin the crankv cases of-the. unitwill. bei compressed by the pistons. Each pistons'a l 45 will continue totravel in advance of its companion piston 48 and-*will 'finally reach' the position. Ashown Ain Fig.. 5.where the ex-V haust .ports32 will be uncovered .to permit.:v thewaste gases. to i escaperfr'om' the cylinders, I' the lgases from'cylinder A passing throughaperture into cylinder B; Shortly-`there-- after thepistons 48 f will', asshQWninFig. 6g reach a position where .the-inlet-ports 31 will be uncovered, so thatthe futili-.charges cases,'mayenterf cylinder-Al and threugh apertureQBN-intocylinder, As all-of the exhaust ports 32 are also open, the advance. of the-.charges throughacylinder Af, and-'into cylinder -B will sweep outv any waste gases.

' that have not' already escaped through-the exhaust ports. While this scavenging operation is occurring, the cranks are passing over their lower dead centers and the pistons occupy the positions shown in Fig. 6.

On account of the arrangement by which the pistons are connected-to' the crank shafts.

l .which are funder- -compression in the "crank-1v leo pistons 45 will then move inwardly ahead of their companion pistons 48 to close the eX- haust ports 32while the inlet ports 3l are f still openas indicated in Fig. 7 'The moving parts of the unit should be so timed that both sets ofexhaust ports 32 will be covered just before'the incoming charges reach these' ports during their progress through the cyl- 'inders Due to the lag of pistons 48 behind pistons 45 during their inward movement',

inlet ports `3l will remain open a suiiicient interval of time after the exhaust ports 32 'have been closed to permit a full charge to be supplied to both of the cylinders. The

pistons48 willfinally cover the inlet ports 31, arid thereafter the pist/ ons moveinwardly on the compressionlstrokehpass over; their 'ointszandireach the posif t1on mdicatedtim amt-Where the'qhel'aeisi ,the cylindersjwill lbe. ignited.4 The inincasso ward movement of the pistons will create a vacuumin each of the crank cases so' that when pistons 45 havey uncovered the vcarburetor ports 34' a charge ofV gas will rush into each crank case from the ycarburetor to be compressed on the next stroke of the pistons.

l@rom the above description it will be seenc that the invention provides a two-strokecycle, opposed-piston engine in'whioh all 0f the exhaust ports'are opened'ahead of the inlet ports on the working stroke and also closed ahead of the inlet ports on the corn-A pression stroke so that pressures higher than that of the atmospheemay be obtained in the cylinders before the compression strokes begin, there being no-loss of compression as in the ca-se of the usual types of engines in which the exhaust' ports cannot be closed until after the inlet ports have been closed on account of the construction of the erigines. A

rlhe arrangement of the two cylinders in parallel relation with a single wall between `them having an' aperture therein, provides for the most effective scavenging of the cylinders, for the incoming charges of compressed gas will rush from the ends of one cylinder, through this aperture and into the other cylinder, withv the result-that all of the residues of combustion that did\not escape when the exhaust ports were lirst uncovered willl be swept out of the cylinders. rlhis improved scavengingv ellect is obtained without theuse of bafllesor other projecting members upon the pistons, so that there are no pockets .in which waste gases may collect,andv 1t 1s not necessary to provide any superuousspace between the inner ends of the pistons to take care of such projecting members. The arrangement by which the pistons are connected to the cranks of the en ine also permits them lto have a slightly onger stroke than would be obtained by a single piston connected to a crank of the same radius.

*While only one unit has been shown and l described above, it will be understood that a complete engine will comprise a number of such units which will be connected to the crank shafts in such angular relations as will` produce the most edective operation. l ln the embodiment of the invention herein shown, the two crank shafts rotatev in opposite directions, but by the' provision of suitable gearing in connection with one of prising a pair of parallel Vcylinders having` the shafts, the members driven by thehafts l may be .rotated in thesame direction. By employing the arrangement shown in my companion application, Serial No. 326,589, tiled concurrently herewith, no such gearing is necessary as the two crank shafts rotate in the same direction. WVhile" the invention has been illustrated in connection with an enginegthat is fired from a spark plug, it should also be understood that the invention is applicable to the Diesel type inlet ports in one cylinder and exhaust ports i in the other cylinder, opposed pistons in each cylinder adapted to control the ports therein,'a pair of crank shafts associated with the cylinders, and adapted to rotate iu opposite directions,- and connectionsy 'between the crank shafts and the'pistons arranged to cause the pistons controlling the inlet ports to lag behind the pistons coi;-

g trolling the exhaust ports during each stroke of the pistons..

2. An internal combustion engine, coinprising a pair of crank shafts adaptedto rotate in,opposite directions, a pair of conrmunicating cylinders arranged between the crank shafts, inlet and exhaust orts in the walls of the cylinders opposedp pistons in each cylinder adapted to control the ports therein, and connections between the pistons and the crank ,shafts arranged to cause the pistons controlling the inlet ports to lag behind the pistons controlling the exhaust ports during each stroke of the pistonsso that the exhaust ports are opened ahead of the inlet ports during the working strokes and closed ahead of the inlet ports durinof the compression strokes,

3. two-stroke-cyc'le internal 4combustion engine, comprising a pair of crank shafts adapted to rotate in opposite directions, a pair of communicatin cylinders arranged between the crank sha ts, inlet and exhaust ports .in the walls of the cylinders, a pair Ithe pistons controlling the inlet ports have uncovered their ports during the working strokesand to cover the exhaust .ports be-1 fore the last-named pistons cover the ports durin the compression stroke.,

4i. n internal combustion engine, coma common dividing wall provided with an aperture midway between the endsy of the cylinders to permit communicating between the cylinders, inlet and exhaust ports .-in the walls of the cylinders, opposed pistons; in eachfcylinder adapted to control the ports therein, power transmitting means adjacent the ends of the cylinders adapted to rotate in opposite directions, and connections ha` l tween the power transmitt' means and the pistons arranged to cause t. e pistons controlling the inlet, ports to lag behind the pistons controlling the exhaust ports during each stroke of the pistons.

5. An internal combustion engine, comf prising a pair of communicating cylinders,

inlet ports in the wall of one cylinder toward the ends thereof, exhaust 'ports in the wall of the other cylinder toward the ends thereof, pistons in the first-named cylinder for controlling the inlet ports therein, pistons in the second-named cylinder for controlling the exhaust ports therein, a

Y crank shaft adjacent each end of the cylinthe cylinders, a pair of pistons in each.

cylinder adapted to control fthe ports therein, a pair of shafts adjacent the ends of the cylinders adapted to rotate in opposite directions, a crank connected .to each shaft, a member .movably mounted von the crank, a rigid connection between one end of the member andone of the pistons of one cylinder, and a movable connection between the other end of the' member and the companion piston ofthe other cylinder, eachfmefmber .incasso v I and the connections between it ,and the corresponding-pistons bein-g so constructed as to cause. te piston controlling the exhaust port .to uncover this port before the' piston controlling the inlet port has uncovered-its port during the working strokes and to cover the exhaust port before the last-named piston covers the 'inlet port during the compression strokes .of the engine.

7. An internal combustion engine, comprising a pair of communicating cylinders, inletY `and exhaust ports in the walls of the cylinders, a pair of pistons in each cylin- .der ladapted to control the ports therein, a pair ,of shafts adjacent the .ends of the cylinders adapted to rotate in .opposite directions, a crank connected lto each shaft, a member movably mounted on leach crank and provided latl one end with `an integral rod connected .to one .of the pistons of one cylinder, a rod pvotally connectedlto .the

.other end of .the member and attached to l the companion ,piston of the other cylinder', the members ,and their .connecting Vnods be ing so arranged .that during rotation voi the shafts both of the pistons controlling the inlet ports will lag behind the pistons controlling the exhaust ports during .each stroke of the pistons so that ,the exhaust ports 

